This invention relates generally to vibratory sound reproduction apparatus and in particular to devices for connecting sound reproduction diaphragms to a fixed baffle or other sound reproduction diaphragms.
If a loudspeaker diaphragm emits sound waves whose wavelengths are comparable to its lateral dimensions, the emitted sound is strongly diminished by the air flowing around the edge of the diaphragm from the front to rear and back again. This flow of air diminishes the build-up of air pressure necessary for sound generation.
To prevent this air flow from occurring, the diaphragm surface is generally extended with a baffle or a box which can be completely closed (air suspension), partially closed (bass reflex) or open in the rear. For these configurations, it becomes necessary to close the space between the moving diaphragm and the baffle or fixed surface so that it is practically air tight. The flexible element which closes this air space is defined as the "surround."
In the apparatus of the prior art, the sound reproduction diaphragms were generally connected to the fixed baffle by means of a corrugated fabric or flexible material which stretched and vibrated with the movable diaphragm. This connecting material also generated various harmonic frequencies and resonant distortions which degrade the sound reproduction fidelity of the system. These resonances must be destroyed to obtain good sound reproduction. The usual prior art technique for for correcting such problems was to impregnate the fabric or coat the material with a sound dampening material such as silicon rubber or other material having a high internal friction.
Generally the materials used are leather, rubber or high viscosity plastics, foam rubber or loose woven cloth impregnated or coated with latex or similar high viscosity semi-liquid components. This damping effect was reflected in the sound reproduction characteristics of the movable diaphragm to limit fidelity.
The damping material as well as the connecting material used in prior art devices also produced its own distortions depending on sound frequency as to whether the individual fibers of the material would cause distortion through rubbing against themselves or as result of harmonic frequencies generated by the material operating in the elastic mode.